Compiles the BPF filtering program written in BPF assembler from a string.

Syntax:

DWORD __stdcall BpfCompileBPFAsmFromStr(HANDLE hFtr, LPCSTR Str);

Parameters:

hFtr

[in] HNUserFilter object handle.

Str

[in] An ASCIIZ string containing BPF assembler program.

Return values:

Description:

This function compiles the program written in BPF assembler to BPF filter. The definitions of the constants previously loaded by BpfCompileBPFDefinesFromFile and BpfCompileBPFDefinesFromStr functions may be used in the program.

Below there is an example of a program in BPF assembler for IP traffic filtering.

char BpfProg[]=
   "#define IP_PROTO   0x800 \n"
   "ld   P[12:2]             \n"  // A = WORD offset 12 (protocol in Ethernet header)
   "jeq  IP_PROTO, 0, Exit   \n"  // If A <> 0x800 (IP) - exit
   "ret  -1                  \n"  // Exit, it is IP packet - return TRUE
   "Exit:                    \n"
   "ret  0                   \n"; // Exit, it is not IP packet - return FALSE